Separator and electrochemical device

ABSTRACT

A separator including a porous substrate and a porous layer. The porous layer is disposed on a surface of the porous substrate and includes inorganic particles and a binder. The porous substrate has an absolute plastic deformation rate in a first direction ranging from about 40% to about 1800%. By using the separator provided in the present application, the safety performance of lithium ion batteries is improved.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/202,346, filed on Nov. 28, 2018, which claimspriority to Chinese Patent Application No. 201810640157.9 filed on Jun.20, 2018, both of which are incorporated by reference in their entirety.

TECHNICAL FIELD

The present application relates to a separator and an electrochemicaldevice, and more particularly to a separator and an electrochemicaldevice using the separator.

DESCRIPTION OF THE RELATED ART

At present, electrochemical devices (for example, batteries) are moreand more widely used and are closely related to people's daily lives.However, the technology concerning the safety of batteries is currentlyunderdeveloped. Occasionally, there have been safety issues where theexplosion of batteries is caused by external forces puncturing thebattery when in use by users. Therefore, with the popularization ofbatteries, users, vendors, and battery manufacturers have put forwardnew requirements for battery safety.

In view of this, there is a need to provide an improved electrochemicaldevice with better safety performance, for example, a lithium ionbattery.

SUMMARY OF THE INVENTION

Embodiments of the present application provide a separator and anelectrochemical device using the separator to solve at least one of theproblems existing in relevant art to some extent. The separator has thecharacteristics of high plastic deformation rate, such that when piercedby a hard object such as a steel nail, the separator around the steelnail will extend together with the steel nail, and eventually create awrapping effect around the steel nail, thereby reducing the probabilityof an internal short circuit and effectively preventing fire caused bylarge-area short circuit inside an electrochemical device (for example,a lithium ion battery).

In an embodiment, the present application provides a separatorincluding: a porous substrate and a porous layer, wherein the porouslayer is disposed on a surface of the porous substrate, the porous layercomprises inorganic particles and a binder, and the porous substrate hasan absolute plastic deformation rate in a first direction ranging fromabout 40% to about 1800%. In some embodiments, the porous substrate hasan absolute plastic deformation rate in the first direction ranging fromabout 40% to about 1600%. In some other embodiments, the poroussubstrate has an absolute plastic deformation rate in the firstdirection ranging from about 40% to about 800%.

According to the embodiments of the present application, the poroussubstrate has an absolute plastic deformation rate in a second directionranging from about 60% to about 1800%. In some embodiments, the poroussubstrate has an absolute plastic deformation rate in the seconddirection ranging from about 70% to about 1600%. In some otherembodiments, the porous substrate has an absolute plastic deformationrate in the second direction ranging from about 70% to about 800%.

According to the embodiments of the present application, the poroussubstrate has a relative plastic deformation rate in the first directionranging from about 50% to about 100%. In some embodiments, the poroussubstrate has a relative plastic deformation rate in the first directionranging from about 65% to about 90%.

According to the embodiments of the present application, the poroussubstrate has a relative plastic deformation rate in the seconddirection ranging from about 60% to about 100%. In some embodiments, theporous substrate has a relative plastic deformation rate in the seconddirection ranging from about 75% to about 90%.

According to the embodiments of the present application, the bindercomprises, but is not limited to, at least one of a vinylidenefluoride-hexafluoropropylene copolymer, a vinylidenefluoride-trichloroethylene copolymer, polymethyl methacrylate,polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, an ethylene-vinyl acetate copolymer,polyimide, polyethylene oxide, cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cyanoethyl amylopectin,cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose,amylopectin, sodium carboxymethyl cellulose, lithium carboxymethylcellulose, an acrylonitrile-styrene-butadiene copolymer, polyvinylalcohol, polyvinyl ether, polytetrafluoroethylene,polyhexafluoropropylene, a styrene-butadiene copolymer, andpolyvinylidene fluoride.

According to the embodiments of the present application, the inorganicparticles comprise, but are not limited to, at least one of alumina,silica, magnesia, titanium oxide, hafnium dioxide, tin oxide, ceriumdioxide, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria,silicon carbide, eboehmite, aluminum hydroxide, magnesium hydroxide,calcium hydroxide and barium sulfate.

According to the embodiments of the present application, the poroussubstrate comprises a polymer film, a multilayer polymer film or anonwoven fabric, wherein the polymer film, the multilayer polymer filmor the nonwoven fabric is formed by any one or more of the followingpolymers: polyethylene, polypropylene, polyethylene terephthalate,polybutylene terephthalate, polyphenylene terephthamide, polyester,polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone,polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole,polyethersulfone, polyphenylene ether, a cyclic olefin copolymer,polyphenylene sulfide and polyethylene naphthalene.

According to the embodiments of the present application, the poroussubstrate has a thickness ranging from about 1 to about 40 μm. In someembodiments, the porous substrate has a thickness ranging from about 3to about 20 μm. In some other embodiments, the porous substrate has athickness of about 7 μm.

According to the embodiments of the present application, the poroussubstrate has a porosity ranging from about 10% to about 70%. In someembodiments, the porous substrate has a porosity ranging from about 15%to about 60%. In some other embodiments, the porous substrate has aporosity ranging from about 25% to about 30%.

In another embodiment, the present application provides anelectrochemical device, comprising a cathode, an anode, and a separatoraccording to the embodiments of the present application.

According to the embodiments of the present application, theelectrochemical device comprises lithium ion batteries.

Additional aspects and advantages of the embodiments of the presentapplication will be partially described and illustrated in the followingdescription or explained by the implementation of the embodiments ofthis application.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings needed for describing the embodiments of the presentapplication or the prior art will be briefly described below tofacilitate the description of the embodiments of the presentapplication. Obviously, the drawings in the following description onlyshow some embodiments of the present application. For those skilled inthe art, the drawings of other embodiments can be obtained according tothe structures illustrated in the drawings without creative efforts.

FIG. 1 is a schematic diagram of a method for testing the plasticdeformation rate of a porous substrate.

FIG. 2 is a schematic diagram showing a nail penetration process of alithium ion battery according to an embodiment of the presentapplication.

EMBODIMENT OF THE PRESENT INVENTION

Embodiments of the present application will be described in detailbelow. In the specification of the present application, the same orsimilar components and components having the same or similar functionsare denoted by like reference numerals. The embodiments described hereinwith respect to the figures are explanatory, and illustrative, and areprovided to facilitate the basic understanding of the application. Theembodiments of the present application should not be construed aslimitations to the present application.

As used in the present application, the term “about” is used to describeand depict minor variations. When used in connection with an event orcircumstance, the term may refer to an example in which the event orcircumstance occurs precisely, and an example in which the event orcircumstance occurs approximately. For example, when used in connectionwith a value, the term may refer to a range of variation less than orequal to ±10% of the numerical value, such as less than or equal to ±5%,less than or equal to ±4%, less than or equal to ±3%, less than or equalto ±2%, less than or equal to ±1%, less than or equal to ±0.5%, lessthan or equal to ±0.1%, or less than or equal to ±0.05%. In addition,amounts, ratios, and other values are sometimes presented in a rangeformat in the present application. It should be understood that such arange format is provided for the sake of convenience and simplicity, andshould be understood flexibly to comprise not only the numerical valuesthat are explicitly defined in the range, but also all the individualvalues or sub-ranges that are comprised in the range, as if each valueand sub-range are explicitly specified.

During the use of lithium ion batteries, there is a risk of beingpunctured by hard objects (such as steel nails) due to improper use.Therefore, in the safety evaluation of lithium ion batteries, a nailpenetration test is employed to characterize the safety of the lithiumion battery under severe operating conditions. The nail penetration testis an important means of characterizing the safety of lithium ionbatteries under extreme operating conditions.

A separator acts to isolate the cathode and the anode in a lithium ionbattery to prevent an internal short circuit, and acts to provide alithium ion exchange channel inside the lithium ion battery at the sametime. When a lithium ion battery is pierced by a nail, the separatorwill be punctured. At this time, a short-circuit area is formed around anail hole, and fire may be more easily caused inside the lithium ionbattery with the increase of the short-circuit area. When a traditionalseparator is punctured, a large tear hole is formed around the nail,causing large-area short circuit in the lithium ion battery, therebycausing a fire. Therefore, improving the reliability of the separatorwhen being pierced by a nail is an effective way to improve the safetyof lithium ion batteries.

For the purposes of the present application, the present applicationprovides a separator and an electrochemical device using the separator,wherein the high plasticity of the separator is characterized by theplastic deformation rate of a porous substrate.

The plastic deformation rate of the porous substrate is tested by themethod shown in FIG. 1. The length before stretching is recorded as L0;the porous substrate of a certain length and width is stretched to breakat a certain rate, and the maximum length reached by the stretching isrecorded as L1; and then the broken porous substrates are docked alongthe fracture and flattened to test the length L2 in a natural state.

The porous substrate is subjected to both elastic deformation andplastic deformation during the tensile test. The amount of elasticdeformation=L1−L2, the amount of plastic deformation=L2−L0, and thetotal amount of deformation=the amount of elastic deformation+the amountof plastic deformation. Plastic deformation is a permanent deformationthat does not bounce back. In the nail penetration test of a lithium ionbattery, the greater the amount of plastic deformation of the poroussubstrate is, the greater the extent that the separator extends with thenail and produces permanent deformation will be, and the better thewrapping effect around the nail will be, thereby maintaining the effectof the separator in isolating the cathode and the anode, and reducingthe probability of failure of lithium ion batteries. On the contrary, ifthe amount of elastic deformation is relatively large, even if theseparator is extended during the piercing process, the separator will begreatly retracted after puncture, thereby weakening the effect of theseparator in isolating the cathode and the anode.

In the present application, the porous substrate has a large plasticdeformation under external force, so that when the separator is piecedby a nail, the separator will have a large extensional deformation withthe nail, thereby maintaining the effect in isolating the cathodes andanodes, preventing the internal short circuit in the lithium ionbattery, and improving the safety of the lithium ion battery. Theabsolute plastic deformation rate cl and the relative plasticdeformation rate ε2 of the porous substrate are calculated by thefollowing equation:

ε1=(L2−L0)/L0×100%

ε2=(L2−L0)/(L1−L0)×100%

In various embodiments of the present application, the porous substratehas an absolute plastic deformation rate in a first direction (e.g. alongitudinal direction) ranging from about 40% to about 1800%. In someembodiments, the porous substrate has an absolute plastic deformationrate in the first direction (e.g. a longitudinal direction) ranging fromabout 40% to about 1600%. In various embodiments of the presentapplication, the porous substrate has a relative plastic deformationrate in the first direction (e.g. a longitudinal direction) ranging fromabout 50% to about 100%. In some embodiments, the porous substrate has arelative plastic deformation rate in the first direction (e.g. alongitudinal direction) ranging from about 65% to about 90%. In variousembodiments of the present application, the porous substrate has anabsolute plastic deformation rate in a second direction (e.g. atransverse direction) ranging from about 60% to about 1800%. In someembodiments, the porous substrate has an absolute plastic deformationrate in the second direction (e.g. a transverse direction) ranging fromabout 70% to about 1600%. In various embodiments of the presentapplication, the porous substrate has a relative plastic deformationrate in the second direction (e.g. a transverse direction) ranging fromabout 60% to about 100%. In some embodiments, the porous substrate has arelative plastic deformation rate in the second direction (e.g. atransverse direction) ranging from about 75% to about 90%. The poroussubstrate having the above properties exhibits a high plasticdeformation rate, and also exhibits a high plastic deformation rate whena porous layer is provided on the surface of the porous substrate.

In various embodiments of the present application, the first directionmay be any direction of the porous substrate, and the second directionis perpendicular to the first direction. In some embodiments, the firstdirection is a transverse direction of the porous substrate, and thesecond direction is a longitudinal direction of the porous substrate. Insome other embodiments, the first direction is a longitudinal directionof the porous substrate, and the second direction is a transversedirection of the porous substrate.

In various embodiments of the present application, the separatorcomprises a porous substrate and a porous layer disposed on at least onesurface of the porous substrate. The porous layer comprises a binder andinorganic particles. The binder contained in the porous layer can notonly bond the inorganic particles together, but also bond the poroussubstrate to the porous layer to achieve integration. The bindercomprises, but is not limited to, at least one of a vinylidenefluoride-hexafluoropropylene copolymer, a vinylidenefluoride-trichloroethylene copolymer, polymethyl methacrylate,polyacrylic acid, polyacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, an ethylene-vinyl acetate copolymer,polyimide, polyethylene oxide, cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cyanoethyl amylopectin,cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose,amylopectin, sodium carboxymethyl cellulose, lithium carboxymethylcellulose, an acrylonitrile-styrene-butadiene copolymer, polyvinylalcohol, polyvinyl ether, polytetrafluoroethylene,polyhexafluoropropylene, a styrene-butadiene copolymer, andpolyvinylidene fluoride.

The inorganic particles used in the present application areelectrochemically stable, that is, they are unable to be oxidized and/orreduced within a driving voltage range (for example, 0 to 5 V based onLi/Li+) of an electrochemical device (for example, a lithium ionbattery). Since inorganic particles having high-density are difficult todisperse in a coating step and may increase the weight of anelectrochemical device (for example, a lithium ion battery) to bemanufactured, inorganic particles having a density as low as possibleare generally used. In various embodiments of the present application,the inorganic particles comprise, but are not limited to, at least oneof alumina, silica, magnesia, titanium oxide, hafnium dioxide, tinoxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide,zirconia, yttria, silicon carbide, eboehmite, aluminum hydroxide,magnesium hydroxide, calcium hydroxide and barium sulfate.

In various embodiments of the present application, the porous substrateof the separator has a thickness ranging from about 1 to about 40 μm. Insome embodiments, the porous substrate of the separator has a thicknessranging from about 3 to about 20 μm. In some other embodiments, theporous substrate of the separator has a thickness of about 7 μm.According to an embodiment of the present application, when the absoluteplastic deformation rate satisfies the requisite of about 40% to about1800%, the nail penetration test passing rate increases with increasingthickness of the porous substrate.

In various embodiments of the present application, the porous substratehas a porosity ranging from about 10% to about 70%. In some embodiments,the porous substrate has a porosity ranging from about 15% to about 60%.In some other embodiments, the porous substrate has a porosity rangingfrom about 25% to about 30%. According to an embodiment of the presentapplication, when the absolute plastic deformation rate satisfies therequisite of about 40% to about 1800%, the nail penetration test passingrate increases with decreasing porosity of the porous substrate.

In various embodiments of the present application, the porous substratecomprises, but is not limited to, a polymer film, a multilayer polymerfilm or a nonwoven fabric, wherein the polymer film, the multilayerpolymer film or the nonwoven fabric is formed by any one or more of thefollowing polymers: polyethylene, polypropylene, polyethyleneterephthalate, polybutylene terephthalate, polyphenylene terephthamide,polyester, polyacetal, polyamide, polycarbonate, polyimide,polyetheretherketone, polyaryletherketone, polyetherimide,polyamideimide, polybenzimidazole, polyethersulfone, polyphenyleneether, a cyclic olefin copolymer, polyphenylene sulfide and polyethylenenaphthalene.

An embodiment of the present application also provides anelectrochemical device including the separator as described above, whichmay be a lithium ion battery. The lithium ion battery comprises acathode containing a cathode active material layer, an anode containingan anode active material layer, an electrolyte, and a separator betweenthe cathode and the anode, where the separator comprises a separator asdescribed above. A cathode current collector may be an aluminum foil ora nickel foil, and an anode current collector may be a copper foil or anickel foil.

In the above lithium ion battery, the cathode active material layercomprises a cathode material capable of absorbing and releasing lithium(Li) (hereinafter, sometimes referred to as “a cathode material capableof absorbing/releasing lithium (Li)”). Examples of the cathode materialcapable of absorbing/releasing lithium (Li) may comprise at least one oflithium cobalt oxide, lithium nickel cobalt manganese oxide, lithiumnickel cobalt aluminum oxide, lithium manganese oxide, lithium manganeseiron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate,lithium iron phosphate, lithium titanium oxide or a lithium-richmanganese-based material.

In the above cathode material, the chemical formula of lithium cobaltoxide may be Li_(x)Co_(a)M1_(b)O_(2-c), where M1 represents at least oneselected from the group consisting of nickel (Ni), manganese (Mn),magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V),chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin(Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum(La), zirconium (Zr) or silicon (Si), and x, a, b and c are respectivelyin the following ranges: 0.8≤x≤1.2, 0.8≤a≤1, 0≤b≤0.2, −0.1≤c≤0.2.

In the above cathode material, the chemical formula of lithium nickelcobalt manganese oxide or lithium nickel cobalt aluminum oxide may beLi_(y)Ni_(d)M2_(e)O_(2-f), where M2 represents at least one selectedfrom the group consisting of cobalt (Co), manganese (Mn), magnesium(Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium(Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn),calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr) or silicon(Si), and y, d, e and f are respectively in the following ranges:0.8≤y≤1.2, 0.3≤d≤0.98, 0.02≤e≤0.7, −0.1≤f≤0.2.

In the above cathode material, the chemical formula of lithium manganeseoxide is Li_(z)Mn_(2-g)M3_(g)O_(4-h), where M3 represents at least oneselected from the group consisting of cobalt (Co), nickel (Ni),magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V),chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin(Sn), calcium (Ca), strontium (Sr) or tungsten (W), and z, g and h arerespectively in the range of 0.8≤z≤1.2, 0≤g<1.0, −0.2≤h≤0.2.

The anode active material layer comprises an anode material capable ofabsorbing and releasing lithium (Li) (hereinafter, sometimes referred toas “an anode material capable of absorbing/releasing lithium (Li)”).Examples of the anode material capable of absorbing/releasing lithium(Li) may comprise carbon materials, metal compounds, oxides, sulfides,lithium nitrides such as LiN₃, metal lithium, and metal and polymermaterials which form an alloy with lithium.

Examples of carbon materials may comprise low graphitized carbon, easilygraphitizable carbon, artificial graphite, natural graphite, mesocarbonmicrobeads, soft carbon, hard carbon, pyrolytic carbon, coke, vitreouscarbon, a sintered body of organic polymer compound, carbon fibers andactivated carbon. Among them, coke may comprise pitch coke, needle cokeand petroleum coke. The sintered body of organic polymer compound refersto a material obtained by calcining and carbonizing a polymer materialsuch as a phenolic plastic or a furan resin at a suitable temperature.Some of these materials are classified into low graphitized carbon oreasily graphitizable carbon. Examples of the polymer material maycomprise polyacetylene and polypyrrole.

Among these anode materials capable of absorbing/releasing lithium (Li),materials whose charge and discharge voltages are close to those ofmetal lithium are selected. This is because the lithium ion batterytends to have a higher energy density with the decreasing of the chargeand discharge voltages of the anode material. The anode material may bea carbon material because its crystal structure is only slightly changedduring charging and discharging. Therefore, good cycle performance andlarge charge and discharge capacities can be achieved. For example,graphite is chosen because it gives a large electrochemical equivalentand a high energy density.

Further, the anode material capable of absorbing/releasing lithium (Li)may comprise elemental lithium metal, metal elements and semimetalelements capable of forming an alloy with lithium (Li), alloys andcompounds including such elements, and the like. For example, they areused with a carbon material. In this case, good cycle performance andhigh energy density can be achieved. In addition to alloys including twoor more metal elements, the alloys used herein also comprise thoseincluding one or more metal elements and one or more semimetal elements.The alloy may be in the form of a solid solution, an eutectic crystal,an intermetallic compound, and a mixture thereof.

Examples of the metal element and the semimetal element may comprise tin(Sn), lead (Pb), aluminum (Al), indium (In), silicon (Si), zinc (Zn),antimony (Sb), bismuth (Bi), Cadmium (Cd), magnesium (Mg), boron (B),gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), zirconium (Zr),ytterbium (Y) or hafnium (Hf). Examples of the above alloys andcompounds may comprise a material having a chemical formula:Ma_(s)Mb_(t)Li_(u) and a material having a chemical formula:Ma_(p)Mc_(q)Md_(r). In these chemical formula, Ma denotes at least oneof a metal element and a semimetal element capable of forming an alloywith lithium; Mb denotes at least one of the metal element and thesemimetal element other than lithium and Ma; Mc denotes at least one ofthe non-metallic elements; Md represents at least one of the metalelement and the semimetal element other than Ma; and s, t, u, p, q, andr satisfy s >0, t≥0, u≥0, p>0, q>0 and r≥0.

In addition, an inorganic compound free of lithium may be used in theanode, for example, MnO₂, V₂O₅, V₆O₁₃, NiS or MoS.

The lithium ion battery further comprises an electrolyte that may be oneor more of a gel electrolyte, a solid electrolyte, and an electrolytesolution, where the electrolyte solution contains a lithium salt and anonaqueous solvent.

The lithium salt is one or more selected from LiPF₆, LiBF₄, LiAsF₆,LiClO₄, LiB(C₆H₅)₄, LiCH₃SO₃, LiCF₃SO₃, LiN(SO₂CF₃)₂, LiC(SO₂CF₃)₃,LiSiF₆, LiBOB, or lithium difluoroborate. For example, the lithium saltis LiPF₆, because it can give high ionic conductivity and improve thecycle performance.

The nonaqueous solvent may be a carbonate compound, a carboxylatecompound, an ether compound, other organic solvents or a combinationthereof.

The carbonate compound may be a chain carbonate compound, a cycliccarbonate compound, a fluorocarbonate compound or a combination thereof.

Examples of the chain carbonate compound comprise diethyl carbonate(DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propylcarbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate(MEC) and a combination thereof. Examples of the cyclic carbonatecompound comprise ethylene carbonate (EC), propylene carbonate (PC),butylene carbonate (BC), vinyl ethylene carbonate (VEC) or a combinationthereof. Examples of the fluorocarbonate compound comprisefluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate,1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate,1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylenecarbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylenecarbonate, trifluoromethylethylene carbonate or a combination thereof.

Examples of the carboxylate compound comprise methyl acetate, ethylacetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethylpropionate, propyl propionate, γ-butyrolactone, decalactone,valerolactone, mevalonolactone, caprolactone, methyl formate or acombination thereof.

Examples of the ether compound comprise dibutyl ether, tetraethyleneglycol dimethyl ether, diethylene glycol dimethyl ether,1,2-dimethoxyethane, 1,2-diethoxyethane, ethoxymethoxyethane,2-methyltetrahydrofuran, tetrahydrofuran or a combination thereof.

Examples of other organic solvents comprise dimethyl sulfoxide,1,2-dioxolane, sulfolane, methyl sulfolane,1,3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide,dimethylformamide, acetonitrile, trimethyl phosphate, triethylphosphate, trioctyl phosphate, and a phosphate or a combination thereof.

Although a lithium ion battery is exemplified above, after reading thisapplication, those skilled in the art will understand that the separatorof the present application can be used in other suitable electrochemicaldevices. Such electrochemical devices comprise any device in which anelectrochemical reaction takes place, and specific examples comprise allkinds of primary batteries, secondary batteries, fuel cells, solarcells, or capacitors. In various examples of the present application,the electrochemical device may be a battery such as a lead acid battery,a nickel-cadmium battery, a nickel-hydrogen battery, a lithium ionbattery, or the like. In particular, the electrochemical device is alithium secondary battery comprising a lithium metal battery, a lithiumion battery, a lithium polymer battery or a lithium ion polymer battery.

Hereinafter, a lithium ion battery is taken as an example and thepreparation of a lithium ion battery is described in conjunction withspecific embodiments. Those skilled in the art will understand that thepreparation methods described in the present application are merelyexemplary, and any other suitable preparation methods also fall withinthe protection scope of the present application.

EXAMPLES

The performance evaluation of the lithium ion batteries in the examplesand comparative examples of the present application is described below.

1. Preparation of Lithium Ion Battery

(1) Preparation of Cathode

The cathode active material lithium cobalt oxide (LiCoO₂), the binderpolyvinylidene fluoride (PVDF), and the conductive agent conductivecarbon black (Super P) were dissolved at a weight ratio of 94:3:3 in thesolvent N-methylpyrrolidone (NMP). The mixture was uniformly stirred toform a cathode slurry, and then the cathode slurry was uniformly coatedon both surfaces of an aluminum foil that was a cathode currentcollector, dried at 85° C., to obtain a cathode active material layer.After cold pressing, slitting, cutting, and welding a cathode tab, acathode was obtained.

(2) Preparation of Anode

The anode active material artificial graphite, the binderstyrene-butadiene rubber, and the conductive agent conductive carbonblack (Super P) were mixed at a weight ratio of 92:3:5 uniformly withdeionized water to form an anode slurry. Then the anode slurry wasuniformly coated on both surfaces of a copper foil that is an anodecurrent collector, and then dried at 85° C. to form an anode activematerial layer. After cold pressing, slitting, cutting, and welding ananode tab, an anode was obtained.

(3) Preparation of Porous Substrate

A PE powder with a molecular weight of 1,000,000 was mixed with paraffinoil at a weight ratio of 1:4, extruded at a high temperature and castedto form a film. The film was stretched in the longitudinal andtransverse directions. The paraffin oil in the film was extracted withdichloromethane, and a porous substrate was obtained after drying andheat setting. By adjusting the stretching ratio in the longitudinal andtransverse directions (stretching ratio), various porous substrates withdifferent plastic deformation rates were obtained.

(4) Preparation of Porous Layer on a Surface of the Porous Substrate

Alumina and polyacrylonitrile were added at a weight ratio of 91:9 todeionized water and mixed uniformly to form a slurry having a solidcontent of 45%. Then the slurry was uniformly coated on one side of theporous substrate by gravure coating to obtain a wet film. After the wetfilm was dried in an oven, the separator of the present application wasobtained.

(5) Preparation of Binder Layer on a Surface of the Separator

PVDF and polyacrylonitrile were uniformly mixed at a weight ratio of 9:1with deionized water, to give a slurry having a final solid content of10% to 15%. Then the slurry was sprayed onto both sides of the separatorprepared in Step (4). After drying in an oven, the final separator wasobtained.

(6) Preparation of Electrolyte Solution

Under a dry argon atmosphere, LiPF₆ was dissolved in a mixed non-aqueoussolvent composed of 30 wt% of ethylene carbonate (EC), 40 wt% of ethylmethyl carbonate (EMC), and 30 wt% of diethyl carbonate (DEC) to give aconcentration of 1.2 M. 1 wt% of ethylene carbonate and 5 wt% offluoroethylene carbonate were added to obtain an electrolytic solution.

(7) Preparation of Lithium Ion Battery

A cathode, the separator obtained in Step (5) and an anode were wound,to obtain an electrode assembly. The electrode assembly was placed in apackage housing, and then the liquid electrolyte was injected andpackaged. After formation, evacuation, and shaping, a lithium ionbattery was formed.

2. Test Methods

(1) Test Method for the Plastic Deformation Rate of the Porous Substrate

The porous substrate was cut into strips having a size of 100 mm×20 mmalong the first direction and the second direction. A region having alength of L0=40 mm was arbitrarily selected in the range of 100 mm inthe length direction of the strip, and marklines were made at two endsof the region. An area between the marklines was stretched to break by ahigh-speed universal tensile testing machine at a speed of 50 mm/min.The maximum length L1 reached by the stretching was recorded, and thenthe broken porous substrate was docked along the fracture and flattenedto test the length L2 in a natural state. The absolute plasticdeformation rate ε1 and the relative plastic deformation rate ε2 of theporous substrate in a certain direction were calculated by the followingformula:

ε1=(L2−L0)/L0×100%

ε2=(L2−L0)/(L1−L0)×100%

(2) Test Method for the Thickness of the Porous Substrate

A length of the porous substrate sample was selected. 10 measurements ofthe thickness of the porous substrate sample were made in an area of5000 mm² by a 1/10000 thickness gauge, and averaged to obtain a valuethat was the thickness of the porous substrate.

(3) Test Method for the Porosity of the Porous Substrate

10 porous substrate samples having a size of 50 mm×100 mm were cut, andthen the 10 porous substrates were placed in a true porosity tester(Model AccuPycII1340) to test the porosity of the porous substrates. Thetrue volumes Vol of the porous substrate samples were determined, andthen the thickness T of the 10 porous substrate samples were determinedby using a 1/10000 thickness gauge. The apparent volume of the poroussubstrate was calculated according to the formula: Volo=50×100×T, thenthe porosity of the separator was calculated by the formula:porosity=(Vol₀−Vol)/Vol₀×100%.

(4) Nail Penetration Test of Lithium Ion Battery

The lithium ion battery was placed in an incubator at 25° C. and stoodfor 30 minutes to allow the lithium ion battery to reach a constanttemperature. The lithium ion battery reaching the constant temperaturewas charged at a constant current of 0.5 C to a voltage of 4.4 V, andthen charged at a constant voltage of 4.4 V until the current reached0.025 C. The fully charged lithium ion battery was transferred to a nailpenetration tester. The ambient test temperature was maintained at 25°C.±2° C., and a steel nail with a diameter of 4 mm was pierced evenlythrough the center of the lithium ion battery at a speed of 30 mm/s andmaintained for 300s therein. If the lithium ion battery did not smoke,did not catch fire, and did not explode, passing was recorded. Each time10 lithium ion batteries were tested, and the number of lithium ionbatteries that pass the nail test was used as an indicator to evaluatethe safety performance of lithium ion batteries.

Conventional lithium ion batteries (Comparative Examples 1-6) andlithium ion batteries according to the embodiments of the presentapplication (Examples 1-40) were prepared and tested according to theabove methods. The porous substrates used in the lithium ion batteriesof the comparative examples and examples were prepared under thefollowing conditions to have the following plastic deformation rate.

Comparative Example 1

The porous substrate had a thickness of 7 μm and a porosity of 30%, hadno porous layer disposed on the surface, and had a stretching ratio inthe longitudinal direction of 7.0 and a stretching ratio in thetransverse direction of 7.0. The obtained porous substrate had anabsolute plastic deformation rate in a first direction of 29%, anabsolute plastic deformation rate in a second direction of 36%, arelative plastic deformation rate in the first direction of 66%, and arelative plastic deformation rate in the second direction of 73%.

Comparative Example 2

The porous substrate had a thickness of 7 μm and a porosity of 31%, hadno porous layer disposed on the surface, and had a stretching ratio inthe longitudinal direction of 7.0 and a stretching ratio in thetransverse direction of 6.8. The obtained porous substrate had anabsolute plastic deformation rate in a first direction of 35%, anabsolute plastic deformation rate in a second direction of 52%, arelative plastic deformation rate in the first direction of 57%, and arelative plastic deformation rate in the second direction of 76%.

Comparative Example 3

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. Duringpreparation, the porous substrate had a stretching ratio in thelongitudinal direction of 7.0 and a stretching ratio in the transversedirection of 6.8. The obtained porous substrate had an absolute plasticdeformation rate in a first direction of 31%, an absolute plasticdeformation rate in a second direction of 47%, a relative plasticdeformation rate in the first direction of 67%, and a relative plasticdeformation rate in the second direction of 75%.

Comparative Example 4

The porous substrate had a thickness of 20 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 7.0and a stretching ratio in the transverse direction of 7.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 30%, an absolute plastic deformation rate in a seconddirection of 51%, a relative plastic deformation rate in the firstdirection of 56%, and a relative plastic deformation rate in the seconddirection of 66%.

Comparative Example 5

The porous substrate had a thickness of 7 μm and a porosity of 15%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 7.0and a stretching ratio in the transverse direction of 7.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 33%, an absolute plastic deformation rate in a seconddirection of 50%, a relative plastic deformation rate in the firstdirection of 52%, and a relative plastic deformation rate in the seconddirection of 60%.

Comparative Example 6

The porous substrate had a thickness of 7 μm and a porosity of 31%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were boehmite, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 7.0and a stretching ratio in the transverse direction of 7.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 36%, an absolute plastic deformation rate in a seconddirection of 55%, a relative plastic deformation rate in the firstdirection of 61%, and a relative plastic deformation rate in the seconddirection of 77%.

Example 1

The porous substrate had a thickness of 7 μm and a porosity of 24%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 2.6and a stretching ratio in the transverse direction of 6.5. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 1600%, an absolute plastic deformation rate in a seconddirection of 68%, a relative plastic deformation rate in the firstdirection of 90%, and a relative plastic deformation rate in the seconddirection of 70%.

Example 2

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 3.2and a stretching ratio in the transverse direction of 6.5. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 1200%, an absolute plastic deformation rate in a seconddirection of 67%, a relative plastic deformation rate in the firstdirection of 90%, and a relative plastic deformation rate in the seconddirection of 72%.

Example 3

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 4.5and a stretching ratio in the transverse direction of 6.5. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 800%, an absolute plastic deformation rate in a seconddirection of 68%, a relative plastic deformation rate in the firstdirection of 89%, and a relative plastic deformation rate in the seconddirection of 71%.

Example 4

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.2and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 676%, an absolute plastic deformation rate in a seconddirection of 69%, a relative plastic deformation rate in the firstdirection of 83%, and a relative plastic deformation rate in the seconddirection of 73%.

Example 5

The porous substrate had a thickness of 7 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.8and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 456%, an absolute plastic deformation rate in a seconddirection of 70%, a relative plastic deformation rate in the firstdirection of 80%, and a relative plastic deformation rate in the seconddirection of 72%.

Example 6

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 70%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 7

The porous substrate had a thickness of 7 μm and a porosity of 31%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 97%, an absolute plastic deformation rate in a seconddirection of 69%, a relative plastic deformation rate in the firstdirection of 67%, and a relative plastic deformation rate in the seconddirection of 77%.

Example 8

The porous substrate had a thickness of 7 μm and a porosity of 31%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.6and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 40%, an absolute plastic deformation rate in a seconddirection of 68%, a relative plastic deformation rate in the firstdirection of 66%, and a relative plastic deformation rate in the seconddirection of 74%.

Example 9

The porous substrate had a thickness of 7 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.5and a stretching ratio in the transverse direction of 2.5. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 235%, an absolute plastic deformation rate in a seconddirection of 1600%, a relative plastic deformation rate in the firstdirection of 77%, and a relative plastic deformation rate in the seconddirection of 90%.

Example 10

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.5and a stretching ratio in the transverse direction of 3.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 232%, an absolute plastic deformation rate in a seconddirection of 1200%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 90%.

Example 11

The porous substrate had a thickness of 7 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.5and a stretching ratio in the transverse direction of 4.5. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 243%, an absolute plastic deformation rate in a seconddirection of 800%, a relative plastic deformation rate in the firstdirection of 77%, and a relative plastic deformation rate in the seconddirection of 88%.

Example 12

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.6and a stretching ratio in the transverse direction of 5.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 235%, an absolute plastic deformation rate in a seconddirection of 687%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 85%.

Example 13

The porous substrate had a thickness of 7 μm and a porosity of 26%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.5and a stretching ratio in the transverse direction of 5.2. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 220%, an absolute plastic deformation rate in a seconddirection of 502%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 85%.

Example 14

The porous substrate had a thickness of 7 μm and a porosity of 29%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.8and a stretching ratio in the transverse direction of 5.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 217%, an absolute plastic deformation rate in a seconddirection of 297%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 82%.

Example 15

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.2. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 228%, an absolute plastic deformation rate in a seconddirection of 163%, a relative plastic deformation rate in the firstdirection of 74%, and a relative plastic deformation rate in the seconddirection of 78%.

Example 16

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 183%, an absolute plastic deformation rate in a seconddirection of 79%, a relative plastic deformation rate in the firstdirection of 65%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 17

The porous substrate had a thickness of 7 μm and a porosity of 24%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 210%, an absolute plastic deformation rate in a seconddirection of 76%, a relative plastic deformation rate in the firstdirection of 71%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 18

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.6and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 430%, an absolute plastic deformation rate in a seconddirection of 75%, a relative plastic deformation rate in the firstdirection of 80%, and a relative plastic deformation rate in the seconddirection of 73%.

Example 19

The porous substrate had a thickness of 7 μm and a porosity of 24%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.2and a stretching ratio in the transverse direction of 6.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 550%, an absolute plastic deformation rate in a seconddirection of 87%, a relative plastic deformation rate in the firstdirection of 86%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 20

The porous substrate had a thickness of 7 μm and a porosity of 23%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 594%, an absolute plastic deformation rate in a seconddirection of 85%, a relative plastic deformation rate in the firstdirection of 90%, and a relative plastic deformation rate in the seconddirection of 74%.

Example 21

The porous substrate had a thickness of 7 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.4. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 220%, an absolute plastic deformation rate in a seconddirection of 92%, a relative plastic deformation rate in the firstdirection of 73%, and a relative plastic deformation rate in the seconddirection of 78%.

Example 22

The porous substrate had a thickness of 7 μm and a porosity of 26%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 198%, an absolute plastic deformation rate in a seconddirection of 210%, a relative plastic deformation rate in the firstdirection of 70%, and a relative plastic deformation rate in the seconddirection of 82%.

Example 23

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.8and a stretching ratio in the transverse direction of 5.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 218%, an absolute plastic deformation rate in a seconddirection of 358%, a relative plastic deformation rate in the firstdirection of 73%, and a relative plastic deformation rate in the seconddirection of 84%.

Example 24

The porous substrate had a thickness of 7 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.8and a stretching ratio in the transverse direction of 5.2. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 239%, an absolute plastic deformation rate in a seconddirection of 398%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 87%.

Example 25

The porous substrate had a thickness of 7 μm and a porosity of 26%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 5.8and a stretching ratio in the transverse direction of 5.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 240%, an absolute plastic deformation rate in a seconddirection of 470%, a relative plastic deformation rate in the firstdirection of 77%, and a relative plastic deformation rate in the seconddirection of 90%.

Example 26

The porous substrate had a thickness of 1 μm and a porosity of 26%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.4and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 150%, an absolute plastic deformation rate in a seconddirection of 70%, a relative plastic deformation rate in the firstdirection of 68%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 27

The porous substrate had a thickness of 3 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 6.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 181%, an absolute plastic deformation rate in a seconddirection of 75%, a relative plastic deformation rate in the firstdirection of 67%, and a relative plastic deformation rate in the seconddirection of 77%.

Example 28

The porous substrate had a thickness of 9 μm and a porosity of 27%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 210%, an absolute plastic deformation rate in a seconddirection of 82%, a relative plastic deformation rate in the firstdirection of 73%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 29

The porous substrate had a thickness of 12 μm and a porosity of 24%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.4. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 233%, an absolute plastic deformation rate in a seconddirection of 89%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 30

The porous substrate had a thickness of 16 μm and a porosity of 25%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 6.4. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 228%, an absolute plastic deformation rate in a seconddirection of 91%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 77%.

Example 31

The porous substrate had a thickness of 20 μm and a porosity of 23%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.4. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 89%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 32

The porous substrate had a thickness of 40 μm and a porosity of 23%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.6. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 247%, an absolute plastic deformation rate in a seconddirection of 93%, a relative plastic deformation rate in the firstdirection of 75%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 33

The porous substrate had a thickness of 7 μm and a porosity of 15%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.4. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 257%, an absolute plastic deformation rate in a seconddirection of 82%, a relative plastic deformation rate in the firstdirection of 77%, and a relative plastic deformation rate in the seconddirection of 77%.

Example 34

The porous substrate had a thickness of 7 μm and a porosity of 46%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 219%, an absolute plastic deformation rate in a seconddirection of 76%, a relative plastic deformation rate in the firstdirection of 73%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 35

The porous substrate had a thickness of 7 μm and a porosity of 60%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 91% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.2and a stretching ratio in the transverse direction of 7.0. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 228%, an absolute plastic deformation rate in a seconddirection of 83%, a relative plastic deformation rate in the firstdirection of 73%, and a relative plastic deformation rate in the seconddirection of 76%.

Example 36

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were boehmite, and theinorganic particles were 85% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 86%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 37

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polymethyl methacrylate, the inorganic particles were Al₂O₃, and theinorganic particles were 70% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 86%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 38

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyvinylidene fluoride, the inorganic particles were Al₂O₃, and theinorganic particles were 70% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 86%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Example 39

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were magnesium hydroxide,and the inorganic particles were 91% by weight of the porous layer. Theporous substrate had a stretching ratio in the longitudinal direction of6.0 and a stretching ratio in the transverse direction of 6.8. Theobtained porous substrate had an absolute plastic deformation rate in afirst direction of 231%, an absolute plastic deformation rate in asecond direction of 86%, a relative plastic deformation rate in thefirst direction of 76%, and a relative plastic deformation rate in thesecond direction of 75%.

Example 40

The porous substrate had a thickness of 7 μm and a porosity of 30%. Thebinder of the porous layer disposed on a surface of the porous substratewas polyacrylonitrile, the inorganic particles were Al₂O₃, and theinorganic particles were 70% by weight of the porous layer. The poroussubstrate had a stretching ratio in the longitudinal direction of 6.0and a stretching ratio in the transverse direction of 6.8. The obtainedporous substrate had an absolute plastic deformation rate in a firstdirection of 231%, an absolute plastic deformation rate in a seconddirection of 86%, a relative plastic deformation rate in the firstdirection of 76%, and a relative plastic deformation rate in the seconddirection of 75%.

Table 1 shows the variable settings and test results for each of thecomparative examples and examples.

The porous substrate of the separator of Comparative Examples 1 and 2had no porous layer. The porous substrate of the separator ofComparative Examples 3-6 had a porous layer on the surface, but theabsolute plastic deformation rate did not satisfy the requisite of about40% to about 1800%. Comparative Examples 4 and 5 show that even if theseparator is thick and the porosity is low, if the absolute plasticdeformation rate does not satisfy the requisite of about 40% to about1800%, the nail penetration test passing rate is still low.

As shown by the data in the sections of “Absolute plastic deformationrate in first direction” (i.e., Examples 1-8) and “Absolute plasticdeformation rate in second direction” (i.e., Examples 6 and 9-15) inTable 1, the greater the absolute plastic deformation rate in the firstdirection (e.g. the longitudinal direction) or the second direction(e.g. the transverse direction) is, the higher the nail penetration testpassing test will be. Compared with Comparative Example 3, the absoluteplastic deformation rate in the first direction or the second directionhas a significant influence on the nail penetration test passing rate.

As shown by the data in the sections of “Relative plastic deformationrate in first direction” (i.e., Examples 6 and 16-20) and “Relativeplastic deformation rate in second direction” (i.e., Examples 6 and21-25) in Table 1, the relative plastic deformation rate in the firstdirection or the second direction is correlated with the absoluteplastic deformation rate in the first direction or the second direction,and its influence on the nail penetration test passing rate complieswith that of the absolute plastic deformation rate on the nailpenetration test passing rate.

As shown by the data in the section of “Thickness of porous substrate”(i.e., Examples 6 and 26-32) in Table 1, the thicker the poroussubstrate of the separator is, the higher the nail penetration testpassing rate will be when the absolute plastic deformation ratesatisfies the requisite. Compared with Comparative Example 4, when theabsolute plastic deformation rate does not satisfy the requisite ofabout 40% to about 1800%, even if the thickness is large, there is noway to effectively improve the nail penetration test passing rate.

As shown by the data in the section of “Porosity of porous substrate”(i.e., Examples 6 and 26-32) in Table 1, the lower the porosity of theporous substrate of the separator is, the higher the nail penetrationtest passing rate will be when the absolute plastic deformation ratesatisfies the requisite. However, compared with Comparative Example 5,when the absolute plastic deformation rate does not satisfy therequisite of about 40% to about 1800%, even if the porosity is low,there is no way to effectively improve the nail penetration test passingrate.

As shown by the data in the section of “Porous layer” (i.e., Examples 6and 36-40) in Table 1, different types of porous layers have nosignificant influence on the nail penetration test passing rate.Compared with Comparative Examples 3 and 6, when the absolute plasticdeformation rate does not satisfy the requisite of about 40% to about1800%, the structure of the porous layer does not have a substantialinfluence on the nail penetration test passing rate.

References throughout the specification to “embodiments,” “partialembodiments,” “one embodiment,” “another example,” “example,” “specificexample” or “partial examples” mean that at least one embodiment orexample of the application comprises specific features, structures,materials or characteristics described in the embodiments or examples.Thus, the descriptions appear throughout the specification, such as “insome embodiments,” “in an embodiment,” “in one embodiment,” “in anotherexample,” “in an example,” “in a particular example” or “for example,”are not necessarily the same embodiment or example in the application.Furthermore, the particular features, structures, materials orcharacteristics herein may be combined in any suitable manner in one ormore embodiments or examples.

While the illustrative embodiments have been shown and described, itwill be understood by those skilled in the art that the embodiments arenot to be construed as limiting the present application, andmodifications, substitutions and changes can be made to the embodimentswithout departing from the spirit and scope of the present application.

TABLE 1 Parameters in examples and comparative examples AbsoluteAbsolute Relative Relative plastic plastic plastic plastic deformationdeformation deformation deformation Thickness rate in the rate in therate in the rate in the of porous first second first second substrateVariable setting Example direction direction direction direction (μm)Absolute plastic 1 1600%  68% 90% 70% 7 deformation rate 2 1200%  67%90% 72% 7 in the first 3 800% 68% 89% 71% 7 direction 4 676% 69% 83% 73%7 5 456% 70% 80% 72% 7 6 231% 70% 76% 75% 7 7  97% 69% 67% 77% 7 8  40%68% 66% 74% 7 Absolute plastic 9 235% 1600%  77% 90% 7 deformation rate10 232% 1200%  75% 90% 7 in the second 11 243% 800%  77% 88% 7 direction12 235% 687%  76% 85% 7 13 220% 502%  75% 85% 7 14 217% 297%  75% 82% 715 228% 163%  74% 78% 7 6 231% 70% 76% 75% 7 Relative plastic 16 183%79% 65% 75% 7 deformation rate 17 210% 76% 71% 75% 7 in the first 6 231%70% 76% 75% 7 direction 18 430% 75% 80% 73% 7 19 550% 87% 86% 75% 7 20594% 85% 90% 74% 7 Relative plastic 6 231% 70% 76% 75% 7 deformationrate 21 220% 92% 73% 78% 7 in the second 22 198% 210%  70% 82% 7direction 23 218% 358%  73% 84% 7 24 239% 398%  75% 87% 7 25 240% 470% 77% 90% 7 Thickness of 26 150% 70% 68% 76% 1 Porous substrate 27 181%75% 67% 77% 3 6 231% 70% 76% 75% 7 28 210% 82% 73% 76% 9 29 233% 89% 75%76% 12 30 228% 91% 75% 77% 16 31 231% 89% 76% 75% 20 32 247% 93% 75% 76%40 Porosity of 33 257% 82% 77% 77% 7 porous substrate 6 231% 70% 76% 75%7 34 219% 76% 73% 76% 7 35 228% 83% 73% 76% 7 Porous layer 6 231% 70%76% 75% 7 36 231% 86% 76% 75% 7 37 231% 86% 76% 75% 7 38 231% 86% 76%75% 7 39 231% 86% 76% 75% 7 40 231% 86% 76% 75% 7 Comparative 1  29% 36%66% 73% 7 Example 2  35% 52% 57% 76% 7 3  31% 47% 67% 75% 7 4  30% 51%56% 66% 20 5  33% 50% 52% 60% 7 6  36% 55% 61% 77% 7 Battery Parametersin examples and comparative examples performance Porosity Nail of porousBinder in porous Inorganic particles penetration test Variable settingsubstrate layer in porous layer passing rate % Absolute plastic 24%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  deformation rate 25%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  in the first 25%Polyacrylonitrile Al₂O₃ (91 wt %) 90% direction 25% PolyacrylonitrileAl₂O₃ (91 wt %) 80% 27% Polyacrylonitrile Al₂O₃ (91 wt %) 70% 30%Polyacrylonitrile Al₂O₃ (91 wt %) 70% 31% Polyacrylonitrile Al₂O₃ (91 wt%) 60% 31% Polyacrylonitrile Al₂O₃ (91 wt %) 50% Absolute plastic 27%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  deformation rate 25%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  in the second 27%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  direction 25% PolyacrylonitrileAl₂O₃ (91 wt %) 90% 26% Polyacrylonitrile Al₂O₃ (91 wt %) 90% 29%Polyacrylonitrile Al₂O₃ (91 wt %) 80% 30% Polyacrylonitrile Al₂O₃ (91 wt%) 70% 30% Polyacrylonitrile Al₂O₃ (91 wt %) 70% Relative plastic 25%Polyacrylonitrile Al₂O₃ (91 wt %) 50% deformation rate 24%Polyacrylonitrile Al₂O₃ (91 wt %) 60% in the first 30% PolyacrylonitrileAl₂O₃ (91 wt %) 70% direction 25% Polyacrylonitrile Al₂O₃ (91 wt %) 80%24% Polyacrylonitrile Al₂O₃ (91 wt %) 90% 23% Polyacrylonitrile Al₂O₃(91 wt %) 90% Relative plastic 30% Polyacrylonitrile Al₂O₃ (91 wt %) 70%deformation rate 27% Polyacrylonitrile Al₂O₃ (91 wt %) 70% in the second26% Polyacrylonitrile Al₂O₃ (91 wt %) 80% direction 25%Polyacrylonitrile Al₂O₃ (91 wt %) 80% 25% Polyacrylonitrile Al₂O₃ (91 wt%) 90% 26% Polyacrylonitrile Al₂O₃ (91 wt %) 90% Thickness of 26%Polyacrylonitrile Al₂O₃ (91 wt %) 30% Porous substrate 27%Polyacrylonitrile Al₂O₃ (91 wt %) 50% 30% Polyacrylonitrile Al₂O₃ (91 wt%) 70% 27% Polyacrylonitrile Al₂O₃ (91 wt %) 80% 24% PolyacrylonitrileAl₂O₃ (91 wt %) 80% 25% Polyacrylonitrile Al₂O₃ (91 wt %) 90% 23%Polyacrylonitrile Al₂O₃ (91 wt %) 100%  23% Polyacrylonitrile Al₂O₃ (91wt %) 100%  Porosity of 15% Polyacrylonitrile Al₂O₃ (91 wt %) 80% poroussubstrate 30% Polyacrylonitrile Al₂O₃ (91 wt %) 70% 46%Polyacrylonitrile Al₂O₃ (91 wt %) 60% 60% Polyacrylonitrile Al₂O₃ (91 wt%) 50% Porous layer 30% Polyacrylonitrile Al₂O₃ (91 wt %) 70% 30%Polyacrylonitrile Boehmite (85 wt %) 80% 30% Polymethyl Al₂O₃ (70 wt %)60% methacrylate 30% Polyvinylidene Al₂O₃ (70 wt %) 60% fluoride 30%Polyacrylonitrile Magnesium 70% hydroxide (91 wt %) 30%Polyacrylonitrile Al₂O₃ (70 wt %) 60% Comparative 30% / /  0% Example31% / /  0% 30% Polyacrylonitrile Al₂O₃ (91 wt %) 10% 30%Polyacrylonitrile Al₂O₃ (91 wt %) 10% 15% Polyacrylonitrile Al₂O₃ (91 wt%) 10% 31% Polyacrylonitrile Boehmite (91 wt %) 10%

What is claimed is:
 1. A separator, comprising: a porous substrate; anda porous layer; wherein the porous layer is disposed on a surface of theporous substrate and comprises inorganic particles and a binder; and theporous substrate has an absolute plastic deformation rate in a firstdirection ranging from about 40% to about 1800%; wherein the absoluteplastic deformation rate is calculated according to an equation(L2−L0)/L0×100%, where L0 refers to a length of the porous substratebefore stretching and L2 refers to a length of the porous substrateafter the porous substrate is stretched to breakage and docked along thefracture caused by the breakage and flattened.
 2. The separatoraccording to claim 1, wherein the porous substrate has an absoluteplastic deformation rate in a second direction ranging from about 60% toabout 1800%.
 3. The separator according to claim 1, wherein the poroussubstrate has at least one of the following properties: an absoluteplastic deformation rate in the first direction ranging from about 40%to about 1600%; and an absolute plastic deformation rate in the seconddirection ranging from about 70% to about 1600%.
 4. The separatoraccording to claim 1, wherein the porous substrate has at least one ofthe following properties: a relative plastic deformation rate in thefirst direction ranging from about 50% to about 100%; and a relativeplastic deformation rate in the second direction ranging from about 60%to about 100%.
 5. The separator according to claim 4, wherein the poroussubstrate has at least one of the following properties: a relativeplastic deformation rate in the first direction ranging from about 65%to about 90%; and a relative plastic deformation rate in the seconddirection ranging from about 75% to about 90%.
 6. The separatoraccording to claim 1, wherein the binder comprises at least one selectedfrom the group consisting of a vinylidene fluoride-hexafluoropropylenecopolymer, a vinylidene fluoride-trichloroethylene copolymer, polymethylmethacrylate, polyacrylic acid, polyacrylate, polyacrylonitrile,polyvinyl pyrrolidone, polyvinyl acetate, an ethylene-vinyl acetatecopolymer, polyimide, polyethylene oxide, cellulose acetate, celluloseacetate butyrate, cellulose acetate propionate, cyanoethyl amylopectin,cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose,amylopectin, sodium carboxymethyl cellulose, lithium carboxymethylcellulose, an acrylonitrile-styrene-butadiene copolymer, polyvinylalcohol, polyvinyl ether, polytetrafluoroethylene,polyhexafluoropropylene, a styrene-butadiene copolymer, andpolyvinylidene fluoride.
 7. The separator according to claim 1, whereinthe inorganic particles comprise at least one selected from the groupconsisting of alumina, silica, magnesia, titanium oxide, hafniumdioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calciumoxide, zirconia, yttria, silicon carbide, eboehmite, aluminum hydroxide,magnesium hydroxide, calcium hydroxide and barium sulfate.
 8. Theseparator according to claim 1, wherein the porous substrate comprises apolymer film, a multilayer polymer film or a nonwoven fabric; whereinthe polymer film, the multilayer polymer film or the nonwoven fabric isformed by any one or more of the following polymers: polyethylene,polypropylene, polyethylene terephthalate, polybutylene terephthalate,polyphenylene terephthamide, polyester, polyacetal, polyamide,polycarbonate, polyimide, polyetheretherketone, polyaryletherketone,polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone,polyphenylene ether, a cyclic olefin copolymer, polyphenylene sulfide orpolyethylene naphthalene.
 9. The separator according to claim 1, whereinthe porous substrate has a thickness ranging from about 1 to about 40μm.
 10. The separator according to claim 1, wherein the porous substratehas a porosity ranging from about 10% to about 70%.